In this YouTube video from an anime 暗殺教室 渚 殺気② t=44s what I hear the character is saying is the following:
戦{たたか}って勝{か}たなくたっていい、殺{ころ}せば勝｛か｝ちなんだ。
I don't understand where the part in bold comes from.
I would guess that it is some variation of the following sentence, but with some additional nuance.
戦って勝たなくていい、殺せば勝ちなんだ。
